German OS 34 36 070 already teaches the provision of a sprung mount using a tubular seat post guided telescopically in the seat tube of the frame, with a compression spring located in the seat tube, on which spring the seat post rests. In order to guide the seat post in a nonrotatable but lengthwise-displaceable manner in the seat tube, the seat tube has an axial slot that extends over the spring travel distance, in which a nose of the seat post engages. This very primitive, known design, however, has the disadvantage that, firstly, a certain amount of lateral play is functionally necessary between the nose of the seat post and the axial guide slot in the seat tube, and therefore a corresponding amount of rotational play of the seat is necessarily provided. This rotational play, however, has a relatively strong influence on the seat because the diameter of the seat post is relatively small, so that the user always has the sensation of sitting on a wobbly seat. Secondly, however, there is considerable friction between the nose of the seat post and the guide slot in the seat tube, which may possibly lead to rattling movements of the spring and, in any event, causes severe wear. The principal cause is that, when the bicycle is being ridden, the seat is stressed alternately from either side because the legs must exert pressure alternately on the pedals and therefore a reactive force with a laterally directed component acts on the seat, with the consequence that the nose is forced alternately against first one side of the slot then the other, creating increased friction there, which is eventually bound to lead to lateral deformation of the slot. Apart from this, the known design also has the disadvantage that rainwater and dirt can penetrate the seat tube through the guide slot and, inside the latter, not only can cause contamination of the spring but especially corrosion thereof, without any advantageous provision for cleaning or remedying the situation.
German Utility Model 88 04 400 proposes a sprung seat post in which the seat support is forked and has two parallel support legs extending symmetrically on either side of the seat post axis, with a spring shock absorber with tubular housing associated with each of said legs, with the two spring shock absorber housings being removable and height-adjustable by means of a clamp mounted on the seat tube. This known sprung seat post remedies the disadvantages of the seat post which is known and described above, because the forked seat support with the spring shock absorbers mounted on either side produces a sprung guidance for the seat which is free of rotational play, producing excellent ride comfort; moreover, the spring shock absorbers are encapsulated in their housings.
The latter sprung seat post represents an excellent technical solution to the stated problem and also exerts an outstanding spring action between the seat and the bicycle frame, with optimum riding comfort for the rider. Its sole disadvantage is that it is relatively expensive to build.